The embryonic neural crest (NC) is the source of many adult cell types including neurons and glia of sympathetic, parasympathetic, enteric, and most sensory ganglia, neuroendocrine cells of the adrenal medulla and thyroid, melanocytes of the skin and irides, connective tissue cells of the head and face, and cells of the aorticopulmonary septum of the heart. Our long term goal is to understand the cellular and molecular mechanisms which govern the generation of this cell diversity, with particular emphasis on neural phenotypes. As one part of this proposal we will continue our in vitro analysis of the developmental differences between NC cell populations isolated by fluorescence activated cell sorting using the monoclonal antibody HNK-1. One aim is to determine the identity of the HNK-1 immunoreactive molecules present on NC cells and their possible functional role in differentiation. A second aim probes how the restriction of developmental potential of the sorted cell populations changes with time. The response of both unsorted and sorted NC cells to defined extracellular matrix components will be studied in a third aim. The active component (s) of the reconstituted basement membrane-like matrix which can enhance adrenergic development in NC cultures will be characterized as a fourth aim. As a second aspect of the proposal we will begin to study the regulation of gene expression during NC development at the mRNA level. One aim in this regard will be to analyze the temporal and spatial expression of mRNA molecules coding for products which are hallmarks of particular pathways of NC differentiation. These experiments will be performed in the presence and absence of extracellular matrix components either known or suspected to alter NC differentiation. Also we will continue our investigation of the structure, expression, and function of an apparently novel cDNA which we have isolated which is expressed during neural development. In addition to their value to developmental neurobiology, these studies may prove relevant to several human congenital disorders in which abnormal NC development has been implicated. These include neurofibromatosis 1, familial dysautonomia, and several craniofacial anomalies. Also, several clinically important tumors including neuroblastomas, pheochromocytomas and melanomas arise as a result of the disruption of normal pathways of NC maturation.